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  <div class="question_difficulty">
   难度：Easy
  </div>
  <div>
   <h1 class="question_title">
    401. Binary Watch
   </h1>
   <p>
    A binary watch has 4 LEDs on the top which represent the
    <b>
     hours
    </b>
    (
    <b>
     0-11
    </b>
    ), and the 6 LEDs on the bottom represent the
    <b>
     minutes
    </b>
    (
    <b>
     0-59
    </b>
    ).
   </p>
   <p>
    Each LED represents a zero or one, with the least significant bit on the right.
   </p>
   <img height="300" src="https://upload.wikimedia.org/wikipedia/commons/8/8b/Binary_clock_samui_moon.jpg">
   <p>
    For example, the above binary watch reads "3:25".
   </p>
   <p>
    Given a non-negative integer
    <i>
     n
    </i>
    which represents the number of LEDs that are currently on, return all possible times the watch could represent.
   </p>
   <p>
    <b>
     Example:
    </b>
   </p>
   <pre>Input: n = 1<br>Return: ["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]</pre>
   <p>
    <b>
     Note:
    </b>
    <br>
   </p>
   <ul>
    <li>
     The order of output does not matter.
    </li>
    <li>
     The hour must not contain a leading zero, for example "01:00" is not valid, it should be "1:00".
    </li>
    <li>
     The minute must be consist of two digits and may contain a leading zero, for example "10:2" is not valid, it should be "10:02".
    </li>
   </ul>
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   <h1 class="question_title">
    401. 二进制手表
   </h1>
   <p>
    二进制手表顶部有 4 个 LED 代表
    <strong>
     小时（0-11）
    </strong>
    ，底部的 6 个 LED 代表
    <strong>
     分钟（0-59）
    </strong>
    。
   </p>
   <p>
    每个 LED 代表一个 0 或 1，最低位在右侧。
   </p>
   <p>
    <img src="https://upload.wikimedia.org/wikipedia/commons/8/8b/Binary_clock_samui_moon.jpg" style="height:300px">
   </p>
   <p>
    例如，上面的二进制手表读取 &ldquo;3:25&rdquo;。
   </p>
   <p>
    给定一个非负整数
    <em>
     n&nbsp;
    </em>
    代表当前 LED 亮着的数量，返回所有可能的时间。
   </p>
   <p>
    <strong>
     案例:
    </strong>
   </p>
   <pre>
输入: n = 1
返回: ["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]</pre>
   <p>
    &nbsp;
   </p>
   <p>
    <strong>
     注意事项:
    </strong>
   </p>
   <ul>
    <li>
     输出的顺序没有要求。
    </li>
    <li>
     小时不会以零开头，比如 &ldquo;01:00&rdquo;&nbsp;是不允许的，应为 &ldquo;1:00&rdquo;。
    </li>
    <li>
     分钟必须由两位数组成，可能会以零开头，比如 &ldquo;10:2&rdquo;&nbsp;是无效的，应为 &ldquo;10:02&rdquo;。
    </li>
   </ul>
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